Editing Quadrature
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+ | [[File:QuadratureEncoder.png|thumb|Basic principle of quadrature encoder which produces quadrature signals when code wheel rotates and detection light passes through segments at different phase.]] | ||
[[File:Quadrature Diagram.svg|thumb|Digital quadrature signals]] | [[File:Quadrature Diagram.svg|thumb|Digital quadrature signals]] | ||
Quadrature digital signals consists two channels (wires) and it can carry incremental setpoint or feedback signal. Quadrature signal is commonly seen in optical encoders which is probably the most common feedback device type in modern servo motors. Quadrature signal can be also used as [[setpoint signal]] and it has similar properties with [[pulse and direction]]. | Quadrature digital signals consists two channels (wires) and it can carry incremental setpoint or feedback signal. Quadrature signal is commonly seen in optical encoders which is probably the most common feedback device type in modern servo motors. Quadrature signal can be also used as [[setpoint signal]] and it has similar properties with [[pulse and direction]]. | ||
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Most optical encoder specify their resolution as pulses per revolution (PPR) which will equal 4X amount of position values per revolution. I.e. 1000 PPR encoder will yield resolution of 4000 counts per revolution. | Most optical encoder specify their resolution as pulses per revolution (PPR) which will equal 4X amount of position values per revolution. I.e. 1000 PPR encoder will yield resolution of 4000 counts per revolution. | ||
==Encoder PPR, CPR, LPR and resolution== | ==Encoder PPR, CPR, LPR and resolution== | ||
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Most encoder suppliers specify quadrature encoder resolution as PPR (pulses per revolution) or LPR (lines per revolution). This specifies how many electrical pulses (0 to 1 transitions) there will be during one revolution. Some manufacturers (such as Avago and USdigital) uses name CPR (counts per revolution) to specify pulses per revolution which may seem counter-intuitive. | Most encoder suppliers specify quadrature encoder resolution as PPR (pulses per revolution) or LPR (lines per revolution). This specifies how many electrical pulses (0 to 1 transitions) there will be during one revolution. Some manufacturers (such as Avago and USdigital) uses name CPR (counts per revolution) to specify pulses per revolution which may seem counter-intuitive. | ||
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| Mechanical servo accuracy including [[tracking error]] || Theoretically 1/8000. In typical case this would yield 1/500 to 1/2000 mechanical accuracy in dynamic conditions (not standing still). | | Mechanical servo accuracy including [[tracking error]] || Theoretically 1/8000. In typical case this would yield 1/500 to 1/2000 mechanical accuracy in dynamic conditions (not standing still). | ||
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